Restoration Commences on 1947 RCA Victor 721TCS

[Kevin Kuehn]

I was taught Canada was part of the American continents, so technically Canadian broadcasts are American too, no?

[Titan1a]

No.

[Kevin Kuehn]

I guess that just goes to show how history is changing, and I'm Old

[Electronic M]

Originally Posted by Kevin Kuehn

I guess that just goes to show how history is changing, and I'm Old

Technically Canada broadcasts in North America making their transmissions a North American broadsact. So Titan1 must think the USA is in South America...

[vortalexfan]

I think what was being meant by the comment is that Canadian broadcasts and US Broadcasts while they are North American broadcasts, Canadian Broadcasts aren't "American" Broadcasts, as in USA broadcasts, (when one uses the word "American" generically like like what Kevin did in his post, you're not specifying which part of North America, because US broadcasts would be referred to as "American Broadcasts" whereas broadcasts in Canada would be referred to as "Canadian Broadcasts".

That's why you shouldn't use such broad sweeping terms when talking about something like that, because you can easily misidentify things (or countries or broadcast standards) by using such generic terminology like that.

What should of been said was: "Aren't Canadian broadcasts technically "North American Broadcasts"? rather than "Aren't Canadian broadcasts technically "American Broadcasts"?

It removes any ambiguity that could be there, especially when you have a country like the US that has the word "America" in its name ("United States of America") and the occupants of said country are called "Americans", and anything associated with said country is called "American", including its television broadcasts.

I hope that explanation was helpful.

[Penthode]

The set and it's electrolytic capacitors are celebrating their 75th anniversary this year. This past week I sadly had to restuff the last wet electrolytic in my 1935 Scott AllWave 23. The wet electrolytic dried up and lost all its capacitance!

I am running the 721TS about five hours a day on weekdays and about four hours overall on weekends. That is about 30 hours per week. No sign of any problem with the original electrolytics.

Incidentally, CHCH TV in Hamilton Ontario is running Andy Griffith, I Love Lucy, Danny Thomas Show, My Three Sons and Bonanza between 10am and 1pm weekdays and the 721TS is on in the background as I work in my office.

Here is Bonanza photographed off air just now.

[Penthode]

This my monthly update on the state of the original electrolytics. And the daily run of the RCA 721TS.

Still running fine. Here is a screen shot of a received morning broadcast just now of the Andy Griffith Show.

[Penthode]

It has been about 5 months since I last reported on the 721TS. Still running fine on the original electrolytics after two years. Only problem with the set is the fine tuning backlash which is from what I see a common fault with the KRK2 tuner. Been running well over 1500 hours now.

Note it is sitting on top of my RCA AR88D receiver.

[stuben]

I just brought home a Crosley 9-408 tv that is all original with no repairs having been previously done. It looks nearly new especially the underside with it's numerous paper/wax capacitors. All the tubes are RCA with date codes ranging from the 11th-22nd week of 1948 with the exception of the two 5U4G's which are Sylvania.

I powered it up on a dimbulb tester with a 250 watt heat lamp and it passed that test. I also have an early RCA 630 TS that I electronically restored with the ever popular "shotgun" method of replacing all the Paper/wax caps and re-stuffing all the electrolytic caps. The set has been working quite well now for four years. While on the dimbulb tester I monitored the current draw with a kill a watt. The Crosley drew only a few watts less than the RCA.

The previous owner said the set worked and provided photographic proof. This mans father is a retired tv tech that fixed old tv's he is nearly 90.

I cautiously powered the set up on a power conditioner for a computer at a line voltage of 120 volts. I also hooked it up to a dvd player and applied a signal. After about 15 seconds I got a raster and after some fiddling with the brightness, horizontal, vertical and contrast I got horizontal and vertical sync and after a minute or so a fairly stable picture that looked quite good! Current draw was 295 watts, about 5 watts less than my RCA. I did not leave the set to run for more than a few minutes fearing that something might give out.

I was quite amazed that this was even possible! All the capacitors, resistors and even wiring looks nearly new. The resistors under the 1B3 have only a little dust and no carbon build up on them. I could even read the color bands easily after brushing the dust away. This set seems to have very few hours on it.

Unfortunately I don't have any tools for trouble shooting radio and tv other than a DMM which can measure resistance, capacitance, inductance, frequency and diode test. I do have a good digital soldering station.

The one job I enjoy the least is re-stuffing the electrolytic cans! After reading much of this thread I am convinced that it may not always be necessary.

Any suggestions? I will try to post some pictures of my set soon.

Thanks in advance!

Paul D.

[Penthode]

I want to emphasize that I never power up electronic equipment of this age without first doing a full electronic assessment. As with the RCA 721TS, I assessed each electrolytic individually by isolating each electrolytic and reforming the dielectric.

I apply a power supply current limited to 10mA maximum and wait until the full rated voltage is met with less than 1 mA leakage. I typically aim for less than 500 uA. If the leakage after a day or so is 1 mA or higher, the capacitor will be replaced/ restuffed.

The 721TS electrolytics all showed leakage well under 500 uA at full rated voltage and tested correct capacity within 10%. I will say that surprised me. But with my six RCA TVs from the late 40's, I have only had to restuff/ replace three electrolytic cans in total.

The problem is suddenly powering them up after a long dormant period without reforming will place undue stress. But I would be game to monitor current leakage over say a week of full rated voltage to see if they survive and if so, I would not hesitate in leaving them in place.

My 721TS has been running on the capacitors for two years now with no sign of failing despite warnings from others.

[Penthode]

Originally Posted by Penthode

21 June, 2020

No sign of any problem with the original electrolytic capacitors since they were reformed. I shall intermittently keep the set on and keep an eye on it.

It has been more than two years running regularly. The original electrolytics remain fine.

I was told the original electrolytics would eventually fail. Any suggestions when this will be?

[Penthode]

Well it has been exactly two years and three months of regular operations. It was June 20, 2020 I first powered it up. It has been running fine ever since. And I am still waiting for those danged original 1947 vintage electrolytic capacitors to fail. There are five of them and they just won't go bad!

I am beside myself because I was sure they were going to fail by now.

Anyhow here is a photo I took a few minutes ago.

[kvflyer]

That's encouraging since I have an RCA 630TS that I purchased a few years ago. It is in great condition; the GE replacement CRT measures NOS. I guess I should bring it up slowly on my Sencore PR-57, monitoring the current and see what happens. I don't mind rebuilding the capacitors but if they hold good, why not???

Thanks for the encouraging update.

[Penthode]

Originally Posted by kvflyer

That's encouraging since I have an RCA 630TS that I purchased a few years ago. It is in great condition; the GE replacement CRT measures NOS. I guess I should bring it up slowly on my Sencore PR-57, monitoring the current and see what happens. I don't mind rebuilding the capacitors but if they hold good, why not???

Thanks for the encouraging update.

You could do it slowly that way. What I prefer is to put a current limited DC power supply across the electrolytics with power off. With the tubes not conducting and with a study of the schematic to see what bleeders are across the B plus, you can better gauge the condition of the electrolytics. In some cases I simply disconnect the electrolytics to better isolate to confirm the condition of the electrolytic.

I have restored set that must have been dormant for 50 years of more. My RCA 721TS the seller near Schenectady NY told me my 721TS was stuch in the attic in the early 60's and was not touched until they sold it to me in 2016. I cleaned out a mouse nest but didn't start to restore it until 2020. It absolutely had not been powered in the meantime so it likely sat unpowered for 60 years. Incredible when you think about it.

And that is what I think saved the electrolytics. I gently brought up the capacitors by limiting the current to no more that about 10mA per capacitor. If the set has sat for decades, the capacitors will be almost a dead short and it is almost certain the capacitors will be destroyed. Yhe key is to carefully monitor and ensure the current is strictly limited until the dielectric has properly reformed.

I would leave the DC supply on for the night and inch the voltage upwards while monitoring the current. When it reached close to the rated maximum voltage, the electrolytic, if healthy, it will draw only about 100uA. If the capacitors draw more than 1mA after reforming, then it must be restuffed.

To summarize, I do not like using a Variac to first power up. To me it is the lazy man approach to the problem and because you are more adequately monitoring the current, it is hit and miss. By using a high voltage DC supply with current and voltage monitoring, you can better decide whether the capacitor is a survivor or not.

Proof should be the 721TS which has lasted over two years on ALL the aluminum can capacitors. I am in the midst of restoring a CT100 color set (which when I have time again in a few weeks will get down to the final alignment) which I slowly reformed the capacitors with the DC supply. All have survived and work fine.

[kvflyer]

Originally Posted by Penthode

You could do it slowly that way. What I prefer is to put a current limited DC power supply across the electrolytics with power off. With the tubes not conducting and with a study of the schematic to see what bleeders are across the B plus, you can better gauge the condition of the electrolytics. In some cases I simply disconnect the electrolytics to better isolate to confirm the condition of the electrolytic....

I have a Heathkit High Voltage Power Supply, IP-17 which I have totally restored. It has voltage and current meters so it would be easy to do.

I have a working T100 that came up on all original electrolytic capacitors. But I have not turned it on for about 8-10 years though. It was rather easy to get going.